Previous code was considering length as bytes, but the API contract
considers the length param to be bits so that the considering `km`
as a VaultKeyManager, the call `km.create_key(ctx, 'AES', 256)` should
generate a 256 bit AES key and not a 2048 bit AES key instead.
Closes-Bug: #1817248
Change-Id: I5815cb74394e18b6058f4c5cf69b656d7cc2c43b
Signed-off-by: Moisés Guimarães de Medeiros <moguimar@redhat.com>